1SD_BUS_PATH_ENCODE(3) sd_bus_path_encode SD_BUS_PATH_ENCODE(3)
2
6 sd_bus_path_encode, sd_bus_path_encode_many, sd_bus_path_decode,
7 sd_bus_path_decode_many - Convert an external identifier into an object
8 path and back
9
11 #include <systemd/sd-bus.h>
12 int sd_bus_path_encode(const char *prefix, const char *external_id,
14 char **ret_path);
15 int sd_bus_path_encode_many(char **out, const char *path_template,
17 ...);
18 int sd_bus_path_decode(const char *path, const char *prefix,
20 char **ret_external_id);
21 int sd_bus_path_decode_many(const char *path,
23 const char *path_template, ...);
24
26 sd_bus_path_encode() and sd_bus_path_decode() convert external
27 identifier strings into object paths and back. These functions are
28 useful to map application-specific string identifiers of any kind into
29 bus object paths in a simple, reversible and safe way.
30 sd_bus_path_encode() takes a bus path prefix and an external identifier
32 string as arguments, plus a place to store the returned bus path
33 string. The bus path prefix must be a valid bus path, starting with a
34 slash "/", and not ending in one. The external identifier string may be
35 in any format, may be the empty string, and has no restrictions on the
36 charset — however, it must always be NUL-terminated. The returned
37 string will be the concatenation of the bus path prefix plus an escaped
38 version of the external identifier string. This operation may be
39 reversed with sd_bus_path_decode(). It is recommended to only use
40 external identifiers that generally require little escaping to be
41 turned into valid bus path identifiers (for example, by sticking to a
42 7-bit ASCII character set), in order to ensure the resulting bus path
43 is still short and easily processed.
44 sd_bus_path_decode() reverses the operation of sd_bus_path_encode() and
46 thus regenerates an external identifier string from a bus path. It
47 takes a bus path and a prefix string, plus a place to store the
48 returned external identifier string. If the bus path does not start
49 with the specified prefix, 0 is returned and the returned string is set
50 to NULL. Otherwise, the string following the prefix is unescaped and
51 returned in the external identifier string.
52 The escaping used will replace all characters which are invalid in a
54 bus object path by "_", followed by a hexadecimal value. As a special
55 case, the empty string will be replaced by a lone "_".
56 sd_bus_path_encode_many() works like its counterpart
58 sd_bus_path_encode(), but takes a path template as argument and encodes
59 multiple labels according to its embedded directives. For each "%"
60 character found in the template, the caller must provide a string via
61 varargs, which will be encoded and embedded at the position of the "%"
62 character. Any other character in the template is copied verbatim into
63 the encoded path.
64 sd_bus_path_decode_many() does the reverse of
66 sd_bus_path_encode_many(). It decodes the passed object path according
67 to the given path template. For each "%" character in the template, the
68 caller must provide an output storage ("char **") via varargs. The
69 decoded label will be stored there. Each "%" character will only match
70 the current label. It will never match across labels. Furthermore, only
71 a single directive is allowed per label. If NULL is passed as output
72 storage, the label is verified but not returned to the caller.
73
75 On success, sd_bus_path_encode() returns positive or 0, and a valid bus
76 path in the return argument. On success, sd_bus_path_decode() returns a
77 positive value if the prefixed matched, or 0 if it did not. If the
78 prefix matched, the external identifier is returned in the return
79 parameter. If it did not match, NULL is returned in the return
80 parameter. On failure, a negative errno-style error number is returned
81 by either function. The returned strings must be free(3)'d by the
82 caller.
83
85 Functions described here are available as a shared library, which can
86 be compiled against and linked to with the libsystemd pkg-config(1)
87 file.
88 The code described here uses getenv(3), which is declared to be not
90 multi-thread-safe. This means that the code calling the functions
91 described here must not call setenv(3) from a parallel thread. It is
92 recommended to only do calls to setenv() from an early phase of the
93 program when no other threads have been started.
94
96 systemd(1), sd-bus(3), free(3)
97systemd 254 SD_BUS_PATH_ENCODE(3)